Our research program investigating drug-drug interactions related to cancer chemotherapeutic agents has shown that tetrahydrocannabinol administered to patients in therapeutic doses does not significantly affect cyclophosphamide or adriamycin pharmacokinetics. Similarly, dimethylsulfoxide does not affect cyclophosphamide plasma pharmacokinetics in lung tumor patients but does affect 24 hour cumulative urinary excretion. Vindesine and cis dichlorodiammine platinum were studied and shown not to affect their respective pharmacokinetics or excretion. Methods have been developed to analyze the glycosidic portions of anthracycline antibiotic molecules as well as 6-thioguanine and metabolites. A new metabolite of 6-thioguanine has been observed in human urine. Ascites fluid is an important reservoir for adriamycin in patients.